So, you’re not going to shock anybody in Québec if you decide to use the expression je suis plein. But if you’d rather avoid it, there are other things you can say that work everywhere French is spoken, like:

If you use these expressions to refuse the offer of more food, you’ll probably want to soften them with other words to avoid seeming rude:

Ah! C’était vraiment délicieux, mais j’ai déjà trop mangé, merci!

You might also hear someone tell you that it’s possible to say je suis rassasié or je suis repu to say that you’re full. I disagree. These expressions are much too formal to be appropriate during a conversation.

Unless you normally say things in English like: “Wow, that BigMac left me replete” or “More pizza? No, thanks, I’m satiated,” then I’d avoid rassasié and repu during conversations in French.

Does je suis plein come from the English “I am full”? I don’t know. But we should consider these points before rushing to label it an anglicism: